Products and process for purifying gases



United States Patent tion of Texas No Drawing. Filed Oct. 2, 1959, Ser. No. 843,914 15 Claims. (Cl. 5529) This invention relates to a series of products and a process for the purifying of gases. More particularly, this invention relates to a series of products and a process for the joint and simultaneous removal of Water, hydrogen sulfide, mercaptans and carbon dioxide from natural and synthetic gas and gas mixtures, such as natural gas, petroleum and gasoline refinery gases, coal gas, water gas, synthesis gas, producer gas, coke oven gas, pipeline gases, et cetera. These gases consist essentially of hydrocarbons, hydrogen, carbon monoxide, nitrogen and mixtures thereof.

A tremendous technology has developed and many hundreds of patents have issued to the present time, describing a multiplicity of products and processes which efiect the dehydration of such gases, the removal of hydrogen sulfide, the removal of mercaptans and the removal of carbon dioxide therefrom. In almost all cases, individual reagents and usually separate treating processes are required to elfect these results.

The basis of my invention is the finding that simultaneous removal of water (i.e. dehydration), removal of hydrogen sulfide, removal of mercaptans and removal of carbon dioxide from gases may be eifected by contacting said gases with at least one member of the group of compounds of the general formula:

where R, R, R" and R are members of the group consisting of hydrogen and methyl.

Compounds of this type are readily prepared by the hydrogenation of the sulfones obtained by the reaction of conjugated drenes of composition with sulfur dioxide. Typical members of this group of composition, suitable for use in the process of this in-.

vention are (d) 2,5 dimethyltetrahydrothiophene -1,1- dioxide (derived from hexadiene-2,4 sulfone), B. Pt. 278-280 C./ 760 mm.

w ll) 2 (e) 3,4 dimethyltetrahydrothiophene -l,1- dioxide (derived from 2,3-dimethylbutadiene sulfone), B. Pt. 274275 0/760 mm.

Methods for the synthesis of these compounds are described by Backer and Bolt, Rec. Trav. Chem. 54, 538- 44 (1935); de Roy and van Zuydewijn, Rec. Trav. Chem. 57, 445-455 (1938); Farlow) (to du Pont), US. Patent 2,233,999 (1941); I. G. Farbenindustrie, French Patent 847,254 (1939); Evans, Morris and Shokal (to Shell), US. Patents 2,360,859 to 2,360,862 (1944); Morris and Van Winkle (to Shell), US. Patent 2,435,404 (1948), and elsewhere.

For simplicity,'the compounds above described will be referred to in this specification by the following abbrevi-ations:

THTD-tetrahy-drothiophenel l -dioxide 3-MTHTD-3-methyltetrahydrothiophene-1,l-dioxide 2-MTHTD-2-methyltetrahydrothiophene-1,l-dioxide 2,5-DiMTI-ITD2,5 dimethyltetrahydrothiophene-1,1-diox de 3,4-DMTHTD3,4 dimethyltetrahydrothiophene-l,l-dioxide The presence of water, water vapor or moisture in many gases, especially such gases as are transported through pipelines over considerable distances (such as natural gas, pipeline gas, etc.) is highly undesirable. There is a tendency for crystalline hydrates to form with some of the components of said gases, which may clog or otherwise inhibit the free flow of the gases. In addition, the higher the moisture content of said gases, the greater will be the corrosivity of these gases on the exposed metallic parts of the pipeline.

The tetrahydrothiophene-1,1-dioxide and the homologues thereof, above described, are highlyhygrosc'opic and will effectively remove the moisture content of gases with which these agents are contacted. Typical vapor pressures of such compounds may be given by the following table.

TABLE I Vapor Pressures of TH TD Temperature, C. Pressure-mm. Hg

The boiling points of typical mixtures of such compounds and water may be given by the following table.

TABLE II Boiling Point of Aqueous Solutions of TH TD at 664 mm.

Percent water by volume: Boiling Point This demonstrates the relative ease with which such solutions, after having absorbed water from gases with 3 which they have been contacted, can be regenerated by distilling off the said water.

The technic of gas dehydration by the use of liquid absorbents for moisture is very well known. As a rule, concentrated solutions of said liquid absorbents are passed countercurrent to the gas being dried down through the contractor, and then through a heat exchange unit to a regenerator where the water removed from the gas is distilled ofl, usually under reduced pressure.

The performance of the tetrahydrothiophene-1,1-dioxide absorbents of this invention may be judged by the depression of the dew points of a typical natural gas treated by the well known procedure of the art. The following table describes the result observed in the treat- It is. not intended in any way to limit this invention in any manner to a specific procedure for the dehydration of gases by the compounds above described, or of regenerating the said absorbent solutions. Any ofthe technics well known in the art may be employed. As a rule, the use of these compounds, in concentrations between 95.0% and 99.5% by weight, at contact temperatures with the gases of fromv 50 F. to 110 F. will produce dew point depressions of between. 45 F. and 105 F.

A 7 lb. gas (ie a gas containing not more than 7 lbs. of water per million standard cubic feet) is usually required for pipeline transmission. Such a gas can be produced with a 65 F. dew'point depression under the conditions given in the following table.

TABLE IV Absorber pressure, p.s.i.a.: Contact temperature, F. 200 68 400 80 60 88 800 93 After the gas hasbeen dehydrated to the-required extent-,- it may be freed of its water content by any of the well known procedures-of the art, e.g. by distilling off the water at', atmospheric pressure, or by vacuum regenera- 7 tion (eg. by, distilling oif the water under reduced pressures of 50 to 400 mm. Hg).

Technics for the dehydration of gases by liquid moisture; absorbents are. described in detail in thereport on Gas Purification appearing in Chemical Engineering for June 15, 1959, and in the- Proceedings of the Gas Conditioning Conference for 1957 (University of Oklahoma).

The tetrahydrothiophene-l,l-dioxide compounds'of this invention are also excellent agents for the removal of hydrogen sulfide from gases. The following table describes the absorption of hydrogen sulfide in a typical compound of this series.

4 TABLE v Gaseous rnl. H28 absorbed per liquid ml. THTD Percent H18 in nitrogen Absorption of H 8 in 3-MTHTD at 760 mm. Hg at F.

Gaseous ml. Percent HiS in methane HES absorbed per liquid m1. 3-MTI-ITD The absorption of hydrogen sulfide by typical tetrahydrothiophene-l,l-dioxide compounds of this series was also determined at advanced pressures, using mixtures of H 8 and nitrogen. The following results were obtained.

TABLE VI Absorption of Hydrogen Sulfide by T etrahydrothioplzene Dioxide Test N o 1 2 3 4 5 ler) 21. 50 12. 25 5. 91 0.95 ml. THTD- 70 50 100 Cale. Total p.s.l.a., 60 F 841.1 759. 2 762. 9 84. 74 S66. 4 'Calc. HzSp.s.i.a., 60 F 282. 7 158. 2 85. 4 43. 2

Total p.s .i.a., 60 F., after absorption 705.4 694.1 727.0 816. 4 858. 5 H28 p.s .i.a., 60 F., after absorption (Cale) 147. 0 93.1 49. 5 12. 2 Mole percent HzS after absorption (Tutweiler) 19. 5 11.9 7.17 3. 41 0. 45 ml. Hrs absorbed/m1.

'IHTD by gage 90 57 45 18 ml. H25 absorbed/n11.

THID by mole ercent... 123 70 52 13 2.6 Moles Hi8 lmoleT TD by gage 0.362 0. 228 0.180 0. 074 Moles Has/mole THTD by mole percent 0. 495 0.282 0.207 0.053 0.010

The tetrahydrothiophene-l,l-dioxide compounds of this invention are also excellent agents for the removal of mercaptans from gases. The following table describes the mercaptan absorbing capacity of a typical compound of this group. A gas mixture of methyl mercaptan in nitrogen was employed.

The ability of the tetrahydrothiophene l,l-dioxide compounds of this invention to remove carbon dioxide from gas streams may be judged by the results reported in the following table:

TABLE VIII Absorption of Carbon Dioxide by Tetrahydrothiophene Dioxide TestNo 1 2 3 4 5 6171819 Total p.s.i.a. before THlD 718.7 719.1 710.5 716.7 701.1 708.3 737.1 682.9 964.1 002, p.s.i.a. before THTD 26.4 42.6 84.9 156.3 205.6 258.1 381.9 533.1 781.9 Mole percent 004 3.2 5.8 11.0 21.4 28.4 37.2 52.9 80.5 86.0 M1. THTD Added- 100.00 100. 100.00 100.00 100. 00 100. 00 100. 00 100.00 100. 00 08.10. Total p.s.i.a 801.5 802.0 792.4 799.3 781.9 789.9 822.1 751.1 1,075.2 Cale. 004 15.15 29.4 47.5 94.7 174.3 229.3 287. 425.9 594 872.0 Total p.s.i.a. After Absor tion" 780.6 790.5 771.2 763.4 743.9 742.1 731.9 660.1 944.9 002 p.s.i.a. After Absorption 14.5 36.0 73.5 138.4 191.3 240.0 335.7 493.0 741.7 Mole percent 002 After Absorption 2. 5 4. 5 9.1 18.0 24. 3 32.1 48. O 76. 7 82. 2 M1. Cozabsorbed/ml. THTD by gage, 8.8 6.8 12.5 21.2 22.4 28.2 53.2 59.9 70.9 Ml. C02 absorbed/ml. THTD by mole 3.5 6.5 10.0 19.8 24.4 32.8 49.4 62.9 87.3 Moles Col/H1016 'lHlD by gage 0. 035 0.027 0.0 0 0.085 0.090 0.113 0.213 0.240 0.308 Moles Cos/mole THTD by Mole perce 0.014 0.026 0.040 0.079 0.098 0.131 0.198 0.252 0.350

All pressures are at 60 13.

All volumes are at 60 1?. and 760 mm. Hg.

The internal volume of the absorption vessel was 967.6 ml.

Mole percent C09, determined by gas analysis (Orsat).

In all cases, the homologous compounds of the series vention, 15% of diethanolamine and 5% of water. The of this invention, i.e. THTD, 3-MTI-1TD, Z-MTHTD, 2,5- flow rate of the inlet gas was 800 s.c.f. per hour and the DMTHTD and 3,4-DMTI-ITD exhibit closely similar solutreating solution flow rate was about 1.0 gal./ min. The bilities for hydrogen sulfide, methyl mercaptan and other inlet gas contained 9.2% carbon dioxide and 2.6% of hymercaptans and carbon dioxide, and are almost equally as drogen sulfide. The treated gas analyzed as follows: efiicient in the removal of water and the depression of the dew 9 of Sand s 00., His grains Dew Point It should be understood that the tetrahydrothiophene-l, Absorbent Percent P 100 9 ig iw l-dioxide and its homologues may be used by themselves, or in admixture with each other, in the purification of THTD 4.4 1.2 76 gases. These may also be used in con1u11ct1on w1th other M L6 go 2-MTHTD- 4. 7 0. 9 84 agents now extensively employed in the pur1ficat1on of 2, 5 DMTHTD 50 L3 70 gases, such as diethylene glycol, triethylene glycol, propyl- 3, 0 72 ene carbonate, monocthanolamine, diethanolamine, N- rnethyldiethanolamine, alkazid (alpha aminoproprionic EXAMPLE 111 et fi t d th t th d t f A natural gas, at a contact pressure of about 800 p.s.i.g. ti n mus b g g f i 5 0 1S mven' was contacted with the various tetrahydrothiophene-l,1- 9 may 6 or P n g O gazes over e dioxide compounds of this invention, in each case as 99% a. e O a ii. p zf composl 40 solutions with 1% of water. The flow rate of the inlet gas Is no 2 i a Hm ion In any mannerfio was 800 8.0.1:. per hour and the treating solution flow rate any specnc emp-vr? ure gr emperaure ragg ny $11891 P was about 1.0 gal./rnir1. The inlet gas contained 8.8% Pressure 01 range 0 pres lires or SP 601 C coinposl' carbon dioxide and 1.4% of hydrogen sulfide. The treated tion of gas or concentration of components in sand gas. gas analyzed as follows. The products of this invention may be used for the punfying of gases under all of the conditions heretofore employed with other agents for the removal of moisture, CO2, msgmms Dew Point dehydration, removal of hydrogen sulfide, mercaptans Absorbent Percent P 100 pgg g and carbon dioxide from said gases.

The following examples are given to define and to il- 1 THTD 5.6 2.0 84 ustrate t is inyentlon 1 ut n no way to 1m1t t to re- 344111111) 12 80 agents, proport1ons or conditions described there1n. Obg-g S g-g 3% -vious modifications and improvements will occur to per- 3;4 DMTHTD j 1 :SOHS skilled in the art.

EXAMPLE I The above gas also contained 11.2 grains per 100 s.c.f.

A natural gas containing 8.2% carbon dioxide and of organically bound sulfur, as methyl mercaptan, ethyl 4.8% hydrogen sulfide (by volume) was contacted at a mercaptan, etc. Under the above conditions, the treated flow rate of 7.5 cu. ft. per hour with the following comgas was freed of its organically bound sulfur to the folpounds of this invention, the latter at a flow rate of 1.0 lowing extents: gal. per hour. The results obtained were as follows:

0 Organic S Content, Outlet Hts-grains Dew Point Absorbent grains per 100 s.c.f., Absorbent Gas,OO2. per 100 s.c.f. Depression, Effluent percent F.

THTD 3.8 THTD 2. 1 4. 2 84 3-1/111111) 4. 0 3-MTH'JD 3. 4 5. 0 78 2-MIHTD-.. 2. 9 2-M'IH1D 2.9 7.1 80 5-DMTHID- 4.2 2, 5DM'1HTD 3. 6 6. 0 68 3,4-DMTHID- 3. 8 3, 4-DM1HTD 2. 8 5.8 72 15% monoethanolamine 85% 0.1 2.9 80 20g i 1i 1 807 THTD 0 1 3 0 75 EXAMPLE IV riet ano amine 20 7%N-Methylethanolaniine 0.1 2.6 81 A Synthesis gas made from coal, analyzing about 6.5% 70 carbon dioxide, 32.5% hydrogen, 50.5% carbon monoxide and 3.5% nitrogen, was contacted at an absorber pressure EXAMPLE II of about 300 p.s.i.g. with the various tetrahydrothiophene- A natural gas, at a contact pressure of about 750 1,1-di0xide compounds of this invention, at the rate of p.s.ig. was contacted with a mixture of 80% of the vari- 2.0 gals. of absorbent per 100 s.c.f. of the raw gas at a oustetrahydrothiophene-1,1-dioxide compounds of this in- 75 temperature of F.

The feed gas contained 450 grains/ 100 s.c.f. of hydrogen sulfide. The treated gas analyzed as follows:

Absorbent H2S-grains 0 02, Percent per 100 cu. ft.

THID 45 3. 4 3-MTHTD 52 3. 8 2-M THTD 50 3. 1 2,5D MTHTD... 48 3. 6 3,4-DMTHTD 52 3. 2

dioxide, 2 methyltetr-ahydrotlriiophene 1,1 dioxide, 2,5- 5

dimethyltetrahydrothiophene 1,1 dioxide and 3,4 dimethyltetrahydrothiophene-1,1-dioxide.

2. The process of claim 1 wherein said'absorbent also contains an ethanolamine.

3. The process of claim 1 wherein said absorbent also contains an =a1kylene glycol.

4. The process ofclaim 1 wherein said absorbent also contains propylene carbonate.

5. The process of claim 1 wherein said absorbent also contains -alpha-amino propionic acid.

6. A process for the removal of hydrogen sulfide from gases of the class consisting essentially of hydrocarbons, hydrogen, carbon monoxide, nitrogen and mixtures thereof containing same, comprising contacting said gases with an absorbent containing at least one member of the group of compounds consisting of tetrahydrothiophene-1,1-dioxide, 3 methyltetrahydrothiophene 1,1 dioxide, 2 methyltetrahydrothiophene 1,1 dioxide, 2,5 dimethyltetrahydrothiophene 1,1 -'dioxide and 3,4 dimethyltetrahydrothiophene-Ll-dioxide.

7. A process for the removal of carbon dioxide from gases of the class consisting essentially of hydrocarbons,

8. A process for the removal of hydrogen sulfide and carbon dioxide from gases of the class consisting essen-- tially of hydrocarbons, hydrogen, carbon monoxide, nitro gen and mixtures thereof containing the same, comprising contacting said gases with an absorbent containing at least one member of the group of compounds consisting of tetrahydrothiophene-l,l-dioxide, 3-methyltetrahydrothiophene-1,1-dioxide, 2 methyltetrahydrothiophene-1,1-

dioxide, 2,5-dimethyltetrahydrothiophene-1, l-dioxide and 3,4-dimethyltetrahydrothiophene-1,1dioxide.

9. The process of claim 8 wherein said gases are con-- tacted with said absorbent at substantially atmospheric temperature.

10. The process of claim 8 wherein said gases are synthesis gases containing hydrogen and carbon monoxide- 11. The process of claim 8 wherein said gases are hydrocarbon-containing gases.

12. The process of claim 8 wherein said gases also contain moisture and the moisture content is reduced by contacting with said absorbent.

1 3,, The process of claim 8 wherein said absorbent also fcont 'ains an ethanolamine selected from the group con sisting of monoethanolamine, diethanolamine, triethanolne and N-methyl derivatives of ethanolamine and dihanolamine.

, 4. A process for the treatment of a wet hydrocarbon gas containing hydrogen sulfide and carbon dioxide as impnrities to place said gas in condition for transportation through pipe lines over a considerable distance, comprising 1 contacting said gas with an adsorbent containing at least one member of the group consisting of tetrahydrothiophene-Ll-dioxide, 3-methyltetrahydrothiophene-1,1-dioxide, Z-methyltetrahydrothiophene-1,1-dioxide, 2,5 -dime'thyltetrahydrothiophene-1,l-dioxide and 3,4-dimethylv tetrahydrothiophene-l,l-dioxide to remove hydrogen sul- Y fide and carbon dioxide to reduce the moisture content of said gas below about seven pounds per million cubic feet.

15. The process of claim 14 wherein said Wet gas is natural gas.

hydrogen, carbon monoxide, nitrogen and mixtures there- 45 of containing same, comprising contacting said gases with an absorbent containing at least one member of the group of compounds consisting of tetrahydrothiophene-1,1-dioxide, 3 methyltetrahydrothiophene 1,1 dioxide, 2- methyltetrahydrothiophene 1,1 dioxide, 2,5 dimethyltetrahydrothiophene 1,1 dioxide and 3,4 d-irnethyltetrahydrothiophene-l,l dioxide.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Apr. 20, 1955 

1. A PROCESS FOR THE SIMULTANEOUS REMOVAL OF HYDROGEN SULFIDE, WATER, CARBON DIOXIDE AND MERCAPTANS FROM GASES OF THE CLASS CONSISTING ESSENTIALLY OF HYDROCARABONS, HYDROGEN, CARBON MONOXIDE, NITRAOGEN AND MIXTURES THEREFO CONTAINING THE SAME AS IMPURITIES, COMPRISING: CONTACTING SAID GASES WITH AN ABSORBENT CONTAINING AT LEAST ONE MEMBER OF THE GROUP OF COMPOUNDS CONSISTING OF TETRAAHYDROTHIOPHEN - 1,1 - DIOXIDE, 3-METHYLTETRAHYDROTHIOPHENE-1,1 DIOXIDE, 2-METHYLTETRAHYDROATHIOPHENE-1,1-DIOXIDE, 2,5DIMETHYLTETRAHYDROTHIOPHENE-1,1-DIOXIDE AND 3.4-DIMETHYLTETRAHYDROTHIOPHENE-1,1-DIOXIDE. 